Why Solange gave Jay Z a beat down

Solange Knowles was already in a bad mood when she got into that elevator with Jay Z and Beyoncé — and an offhand comment by her brother-in-law just made things worse.

It's a mystery that was set to surpass that of "Who killed Tupac and Biggie?" Everyone wants to know #whatjayzsaidtosolange in that elevator to make her go nuts on him. While the three main players — Jay Z, Solange and Beyoncé — aren't talking, sources close to the situation are, and they are painting a picture of a typical family feud and a sister-in-law who should probably mind her own business.

An insider told The New York Daily News that trouble started earlier in the night when non-celeb pals of Solange tried to crash the Met Ball by dropping Jay-Z's name.

"They were pretending they were guests of his and not hers. Management went to Julius (Beyoncé's bodyguard) and said there's a problem," the source said.

Hova told her to knock it off, setting the mood for the rest of the night.

Solange then got into it with Rachel Roy, according to onlookers. "Solange was provoked by Rachel," a witness told People, with another adding that Bey's little sis was "yelling at other people in the party."

But the straw that broke the camel's back was when Jay Z decided to go to Rihanna's after party while Bey went home.

"[Solange] seemed drunk and irritated," another pal told The Daily News. "She said, 'Why can't you go home?' and to Beyoncé, 'Why does your husband need to go to the club right now?'"

Jay Z basically told her to mind her own business. "You're one to talk," he replied, according to the source — and that's when all hell broke loose.

"Jay said something inappropriate to Beyoncé and Solange, and she snapped," another insider told People. "When they got in the elevator, it escalated quickly the way family tensions can. It got exceptionally heated the way family moments can."